Figure 1.

Expression of destabilizing mutants and wild-type LacZ. (a) SDS-PAGE of soluble and insoluble fractions of cells expressing WT LacZ and five destabilizing
mutants induced with 10 μM IPTG. (b) Total β-galactosidase at different times after IPTG induction. The LacZ band is indicated
by the black arrow. (c) Relative synthesis rate of β-galactosidase. P-values were obtained using a t-test of the linear regression slopes based on quantification of the gel images. Error
bars represent the standard error of the regression slopes. (d) GroEL western blots in cells exprerssing WT and LacZ mutants. S, soluble fraction;
I, insoluble fraction; '-', no IPTG; '+', 20 μM IPTG; Δ, heat shock (1 h shift from
37 to 42°C).